This invention is generally directed to toner and developer compositions, and more specifically to toner compositions comprised of amorphous ternary copolycarbonates. In one embodiment of the present invention the toner composition, which is particularly useful in flash fusing and other noncontact fusing processes, is comprised of amorphous ternary copolycarbonates, pigment particles, and additive components, inclusive of charge enhancing additives thereby enabling the toner composition to acquire a positive, or negative triboelectric charging value. The aforementioned toner compositions when selected for incorporation into xerographic imaging apparatuses permit images of excellent resolution with no background deposits for an extended number of imaging cycles, subsequent to, for example, subjecting the developed image to noncontact fusing such as a flash fusing process, wherein there can be selected a xenon lamp providing a 1.1 microsecond pulse duration with a linearly varying pulse intensity along the surface being exposed. In addition, fused images of excellent resolution without odor or effluent and with a low fusing energy of, for example, about 0.85.+-.0.05 Joules/cm.sup.2 can be obtained with the compositions of the present invention. Moreover, one of the main advantages associated with the aforementioned toner compositions resides in their thermal stability in the range of, for example, from about 250.degree. C. to about 320.degree. C. thereby avoiding the formation of odors, or undesirable effluents during flash fusing or radiation fusing.
The formation and development of images on the surface of photoreceptors, for example, by electrostatic means is well known, these processes involving subjecting the photoconductive material to a uniform charge; and subsequently exposing the surface thereof to a light image of the original to be reproduced. The latent image formed on the xerographic photoconductive surface is developed with toner particles specifically prepared for this purpose. Thereafter, the developed image can be transferred to a final support material such as paper, and affixed thereto to obtain a permanent record or copy of the original. Numerous methods are known for applying the electrostatic toner particles to the electrostatic latent image including, for example, cascade development, magnetic brush development, powder cloud development and touchdown development.
Thereafter, the developed image can be fixed by a number of various well known techniques including, for example, vapor fixing, heat fixing, pressure fixing, or combinations thereof, as described, for example, in U.S. Pat. No. 3,539,161. These techniques of fixing, while suitable for certain purposes, suffer from some deficiencies thereby rendering their use either impractical or difficult for specific electrostatographic applications. For example, it is difficult to construct an entirely satisfactory heat fuser which has high efficiency, can be easily controlled, and has a desirable short warm-up time. Also, heat fusers sometimes burn or scorch the support material. Somewhat similar problems including, for example, image offsetting and undesirable resolution degradation, are present with pressure fusing methods. Additionally, with these processes consistently desirable permanent images are not obtained. Further, although vapor fixing has advantages, one of its main disadvantages is that a toxic solvent is used, therefore, in many situations this method becomes commercially unattractive because of health hazards associated therewith. Also, equipment and apparatus to sufficiently isolate the fuser in vapor processes from the surrounding area are very complex, costly and difficult to operate.
Many of the modern electrostatographic reproducing apparatuses, which are capable of producing copies at an extremely rapid rate, created the need for the development of new materials and processing techniques. With these systems, radiant or flash fusing fixing processes can be selected wherein the energy which is emitted in the form of electromagnetic waves is immediately available and requires no intervening medium for its propagation. Although an extremely rapid transfer of energy between the source and the receiving body is provided with the flash fusing process, a problem encountered with this process resides in obtaining an apparatus which can fully and efficiently utilize a preponderance of the radiant energy emitted by the source during a relatively short flash. The toner image in these systems usually comprises a radiant energy causing most of the energy generated to be wasted as it is transmitted to the image, or is reflected away from the fusing areas. Furthermore, many of the toner compositions currently available, particularly colored toner compositions, contain pigments which do not absorb energy in the near infrared region of the spectrum thereby necessitating the supply of larger amounts of energy to these compositions to affect fusing. Moreover, many of the known colored toner compositions contain pigments therein which do not absorb energy in the near infrared and/or ultraviolet region of the spectrum, thus only about 33 percent of the spectral energy generated, for example, from presently used Xenon lamps is desirably absorbed by the colorants contained in the toner composition.
Specifically, for example, radiation energy emitted from a Xenon flash lamp or similar source is absorbed by the pigment or dye contained in the toner composition; and thereafter, this energy is converted to thermal energy by a radiationless decay process enabling heat generation causing the particles to fuse. The flash energy used is absorbed in a layer of toner of finite thickness adjoining the outer toner surface with absorption being greatest at the surface. This energy is also constantly decreasing with increasing distance from the outer toner surface. The flash generated is of very short duration, on the order of about one millisecond; and consequently, the toner regions very close to the surface are heated to a much higher temperature than the toner mass as a whole.
Additionally, it is known to incorporate into toner compositions various charge enhancing additives, such as alkyl pyridinium halides, reference U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference; distearyl dimethyl ammonium methyl sulfates, reference U.S. Pat. No. 4,560,635; organic sulfonate and sulfates, reference U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference; specific quaternary ammonium salts; and the like. Also, there is illustrated in U.S. Pat. No. 4,460,672, the disclosure of which is totally incorporated herein by reference, a developer composition mixture comprised of electrostatic toner particles consisting of resin particles, pigment particles, a waxy material with a molecular weight of from about 500 to about 20,000, and further included in the composition from about 0.5 percent by weight to about 10 percent by weight of a charge enhancing additive selected from, for example, alkyl pyridinium halides, organic sulfonate compositions, and organic sulfate compositions.
Furthermore, it is known to incorporate into toner compositions various resins such as addition polymers or polycondensation polymers which are thermally stable and do not produce odor or effluent during radiation or flash fusing process. It is also known that polycarbonate resins are thermally stable, however, their thermal and rheological properties render them undesirable in some instances for use in toner compositions. Therefore, a polycarbonate with the appropriate thermal and rheological properties is needed for incorporation into toner compositions.
There are also described in other patents toner compositions with wax components therein, reference for example U.S. Pat. No. 4,556,624, the disclosure of which is totally incorporated herein by reference. Specifically, the aforementioned patent illustrates an improved positively charged electrostatic toner composition comprised of a polyblend mixture of a crosslinked copolymer composition; and a second polymer, pigment particles, a wax component of a molecular weight of from about 500 to about 20,000, and a charge enhancing additive. Other patents of interest include U.S. Pat. No. 3,079,342, relating to toners comprised of polystyrene and polymeric modifiers incorporated therein such as long chain thermoplastic plasticizers; U.S. Pat. No. 4,329,415, relating to magnetic developer compositions with waxes therein such as vegetable waxes, whale wax and synthetic waxes including polyethylene wax, and polypropylene wax; U.S. Pat. No. 4,362,803, describing one component magnetic developers with low molecular weight polyethylene and polypropylene; and U.S. Pat. No. 4,385,107, disclosing toner compositions comprised of specific graft copolymers inclusive of polyethylene and polyproplyene.
In addition, there are illustrated in U.S. Pat. No. 4,543,313 toner compositions comprised of resin particles selected from the group consisting of thermotropic liquid crystalline polycarbonates, copolycarbonates, polyurethanes, polyesters, and copolyesters; and pigment particles. However, these particles are not amorphous, for example, and possess two or more thermal transitions as compared to the amorphous ternary copolycarbonates of the present invention with only a single thermal transition temperature of from about 50.degree. C. to about 55.degree. C. Furthermore, in U.S. Pat. No. 4,318,974 there is disclosed an improved toner composition comprised of a colorant and a copolycarbonate resin wherein the resulting toner has certain characteristics, reference the Abstract of the Disclosure, and note the disclosure in column 3, beginning at line 51. Furthermore, other patents that are primarily of background interest include U.S. Pat. Nos. 3,694,359; 4,288,516; 4,352,877; 4,457,998; 4,555,468 and 4,575,478.
Nevertheless, there remains a need for toner and developer compositions particularly useful in electrostatographic imaging systems having incorporated therein flash fusing devices. Also, there is a need for resins with low melt viscosities of, for example, from about 100 to about 300 poise at 150.degree. C. and specific glass transition temperatures, for example above 50.degree. C., or in excess of the blocking temperature of the specific toner composition selected. Furthermore, there is a need for thermally stable resins which withstand temperatures as high as 320.degree. C. without generating effluents or odors. Also, there is a need for positively charged toner compositions containing therein in addition to the ternary copolycarbonates illustrated herein pigment particles, and charge enhancing additive components. Moreover, there is a need for thermally stable toner compositions with acceptable triboelectric charging properties, which compositions are especially useful in electrostatographic imaging devices containing therein flash fusing components, such as xenon lamps. Another need of the present invention resides in the provision of processes wherein the developed image formulated is permanently affixed to a suitable substrate by a flash fusing process emitting energy in an amount of from about 4 to about 8 joules/inches squared. There also remains a need for toner compositions that are thermally stable up to temperatures of 350.degree. C. without generating odor or effluent during the fusing process.